Thank you for your answer Niklas, have you an idea of what the Sevap in the Rho equation contains ?

Sevap += dieselSpray.evaporationSource(i);

My 0D model have not time for the moment, it caculate only the properties of droplets at the equilibrium state, it doesn't assume a D2 law or Abramzon model, i use the secant methode to calculate these properties.

So if i know what Sevap contains, i think that i can implement it..

thank you

niklas

June 14, 2011 04:03

I suspected that you would say that :)

actually you can relate your model to a characteristic time and use the existing
framework to add your new evaporation model.

in FOAM the mass of the droplet is calculated/updated according to this equation

Code:

(m^n - m^{n-1}) m^n
--------------------- = - -------- (1)
dt tau

where m^n is the new mass that the drop will have at this time-step and m^{n-1} is the previous drop mass.
dt is the integration step and tau is the characteristic evaporation time (evaporation model)

if you know that the mass of the drop is updated according to this equation,
you can calculate the new mass, m^n, according to your equilibrium conditions and related that to tau.

This way you dont have to calculate the source terms and bother with Sevap as it will be handled
automatically.

Tag

June 14, 2011 05:24

thank you Niklas,

I think it's easier to do that, I will keep you informed on the progress of my implementation.

i will haves somme questions about the mass fraction of the liquids phase and gazous phase, temperature, pressure modification and updating ...

Thank you again Niklas....

Noureddine.

Tag

June 24, 2011 10:32

Hii Niklas,

I have successfully implemented my 0D model in OpenFoam as you suggest.

for the case of standartEvaporationModel and my 0D evaporation model:
i want to know how the temperature and other properties like volume fraction and the diameter of the droplets are calculated and updated, I suspect that the B term in evaporation model is considered constant.

Thank you.

niklas

June 25, 2011 08:00

Great,

Im not following, which B-term?

if you want to find out how these properties are updated, just check the updateProperties-function in parcel.C.

Tag

June 29, 2011 07:55

Dear Niklas,

B is the Spalding mass number.

I have to give the initial mass fractions of the liquide, gaz, N2 and O2 (air) and their temperatures in cell to my 0Dmodel that calculate the equilibrium temperature and then the final mass fractions of these species in the same cell, in order to estimate the mass ratio of the liquide : m (n)/m(n-1)= Yl(n)/Yl(n-1) (Yl mass fraction of liquide). the problème that i don't found yet these propertise in openfoam.

Can you give me an idea to how i do that ?

Thank's.....

Tag

July 4, 2011 05:27

Hi,

where can i find the total mass, the gas temperature, the fractions of different species in cell(i), i had to use these properties in one class that I've created in dieselSpray SubModels.

Thank U.

niklas

July 4, 2011 05:59

Have you checked parcel.C?

All is in there.

if you want the mass of the cell you have to get the density and cell volume

i have already seen this in standardEvaporationModel.C, Xs is a variable of the relaxationTime function, but when this function is used we must give the Xs that is, i think is calculated by another function or expression, this is what i want to know.

thank you.

niklas

July 5, 2011 02:27

Ah, OK.

Thats done in parcel/setRelaxationTimes.C

However, Xs just calls the function which is defined in the liquidMixture class
thermophysicalModels/liquidMixture/liquidMixture/liquidMixture.C